Development of Impact Testing Machine and of Non-destractive Characterization Technic for Sintered Tool Materials

点击翻译按钮获取中文摘要

As cutting edge chipping is one of the most troublesome problems in machining practice, it is required to establish the system which enables to predict the chippig. The system eatablished needs two major informations, one is the stress and temperature distributions within cutting edge which are determined by the cutting conditions. The other is the fracture characteristics and thier changes of tool material under practical cutting conditions. This profect proposes the method to obtain the lather informations.In order to obtain the behavior of fracture characteristics and their changes of sintered tool materials under such conditons that are encountered in interrupted cutting operations, both of the impact tension and compression loading testing machine must be specially developed, in which a control of loading rate or a rising time of load and temperature as well as applied stress and cycles are arbitrarily possible.The results obtained by the developed testing machine are sumerized as … More follow: For carbide material P20(1) The carbides, considered as extremely brittle material, are also deteriorated by cyclic loading like a fatigue seen in a ductile material. The fracture stress decreases with increase of impact stress and cycle.(2) The deterioration rate greatly depends on the loading rate. The impact loading gives larger deterioration than the slow one.(3) The threshold stresses are found in both impact tension and compression deterioration stresses.(4) The fracture stress decreases monotonously with temperature rise, however at all temperature less than 800゜C brittle fracture may be seen.(5) Temperature plays no important effect on the deterioration of carbide material. For sintered ceramic <Al_2> <O_3>(6) The ceramic is also deteriorated by repetition of impact stress as same manner that the sintered carbide P20.(7) The fracture stress does not decrease monotonously with temperature rise, but the maximum fracture stress and also the fracture like a ductile manner are seen at about 850゜C.(8) The effect of temperature on deterioration is very large. The fracture stresses decrease extremely and they scatter in very wide range.Finally, non-destructive characterization method of deterioration level is discussed. It is clear that the progress of deterioration gives an increase of attenuation of ultrasonic wave in the material, however at this stage the quantitative relation of the deterioration level and the attenuation can not seen. The reason may be considered that the attenuation in a contact layer between specimen and detector can not be fixed. Less